Dermatopathology Practice Questions

Q: HMB 45 is a tumor marker for which of the following neoplasms?

Malignant melanoma. **Explanation:** **HMB-45 (Human Melanoma Black-45)** is a highly specific monoclonal antibody used in immunohistochemistry (IHC). It reacts against **gp100**, a cytotoxic transmembrane glycoprotein found in **pre-melanosomes** (specifically stages I and II). 1. **Why Malignant Melanoma is correct:** Malignant melanoma is a neoplasm of melanocytes. Since HMB-45 targets the premelanosome vesicle, it shows high positivity in melanoma cells [1]. While S-100 is more sensitive for melanoma, **HMB-45 is more specific**, making it the gold standard for confirming the diagnosis and differentiating it from other "small round blue cell tumors" or poorly differentiated carcinomas [1]. 2. **Why other options are incorrect:** * **Mesothelioma:** The characteristic markers are **Calretinin**, WT-1, and Cytokeratin 5/6. * **Bronchogenic Carcinoma:** Adenocarcinomas of the lung typically express **TTF-1** (Thyroid Transcription Factor-1) and Napsin A. * **Pancreatic Carcinoma:** These usually express CA 19-9 (serum marker) and CEA or Cytokeratins (IHC). **High-Yield Clinical Pearls for NEET-PG:** * **S-100:** Most sensitive marker for melanoma (but lacks specificity as it is also positive in neural tumors and liposarcomas). * **Melan-A (MART-1):** Another highly specific marker for melanocytic differentiation. * **SOX10:** A nuclear marker gaining popularity for its high sensitivity and specificity in spindle cell and desmoplastic melanomas. * **HMB-45 Exception:** It is also positive in **Angiomyolipoma (AML)**, as AML belongs to the PEComa (Perivascular Epithelioid Cell tumor) family. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1151-1152.

Q: The skin biopsy shown below is most consistent with which of the following conditions? ![img-28.jpeg](img-28.jpeg)

Lichen planus. ***Lichen planus*** - The image shows **basal cell degeneration** (liquefaction degeneration), a **sawtooth rete ridge pattern**, and a band-like inflammatory infiltrate primarily composed of lymphocytes at the dermo-epidermal junction, which are classic histological features of **lichen planus**. - **Civatte bodies** (apoptotic keratinocytes forming colloid bodies) are typically present, resulting from keratinocyte damage at the basal layer. - These features make lichen planus the most consistent diagnosis. *Lichen nitidus* - Characterized by **"ball and claw" lesions**, which are small, localized epidermal invaginations enclosing a central infiltrate of lymphocytes and histiocytes. - The granulomatous infiltrate is more focal and circumscribed compared to the band-like pattern of lichen planus. - While both are interface dermatitides, the architectural pattern differs significantly. *Morphea* - This is a localized form of **scleroderma**, characterized by increased **collagen deposition**, thickening of the dermis, and loss of adnexal structures like hair follicles and sweat glands. - The inflammatory infiltrate is typically perivascular and interstitial, not band-like at the dermo-epidermal junction. - The image does not show features of dermal fibrosis or homogenization of collagen bundles expected in morphea. *Lupus erythematosus* - Also shows **interface dermatitis** with basal vacuolar changes and lymphocytic infiltrate. - However, lupus typically shows a **perivascular and periappendageal pattern** of infiltrate rather than the dense band-like pattern of lichen planus. - Additional features in lupus include dermal mucin deposition, thickened basement membrane (PAS-positive), and follicular plugging. - The dense, continuous band-like infiltrate and sawtooth rete ridges favor lichen planus over lupus.

Q: A child presents with multiple skin lesions over the inner thigh and genital areas. It initially started as macule and later developed to become nodules. Some nodules have central umbilication. The histology of the lesion is shown below

Henderson-Patterson bodies. ***Henderson-Patterson bodies*** - The clinical description of **umbilicated nodules** in the genital area of a child is characteristic of **molluscum contagiosum** [1], [2]. - **Henderson-Patterson bodies** are large eosinophilic, intracytoplasmic inclusions seen in cells infected with the **molluscum contagiosum virus** [2]. *Guarnieri bodies* - **Guarnieri bodies** are eosinophilic, intracytoplasmic inclusions found in cells infected with the **variola virus** (smallpox). - While they are also viral inclusions bodies, they are associated with a different viral disease that does not typically present as umbilicated nodules in this manner. *Cowdry type A inclusion bodies* - **Cowdry type A inclusion bodies** are intranuclear inclusions characteristic of **herpes simplex virus** (HSV) and **varicella-zoster virus** (VZV) infections. - Herpes lesions are typically **vesicular** and painful, not umbilicated nodules like molluscum contagiosum. *Negri bodies* - **Negri bodies** are pathognomonic eosinophilic inclusions found in the cytoplasm of nerve cells in individuals infected with the **rabies virus**. - Rabies presents with neurological symptoms after a bite from an infected animal, which is distinctly different from the described skin lesions. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 997-998. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1177-1180.

Q: Which of the following structures is pathognomonic for chromoblastomycosis?

Sclerotic body. ***Sclerotic body*** - **Sclerotic bodies**, also known as **Medlar bodies** or **fumagoid cells**, are characteristic coin-shaped, thick-walled, septate, dematiaceous structures observed histologically in affected tissues. - Their presence is **pathognomonic** for chromoblastomycosis, a chronic fungal infection of the skin and subcutaneous tissue. *Asteroid body* - **Asteroid bodies** are typically found in **sporotrichosis**, representing an antigen-antibody complex surrounding fungal elements. - They are not characteristic of chromoblastomycosis. *Budding yeast* - **Budding yeast** forms are commonly seen in various fungal infections, such as **candidiasis** or **cryptococcosis**, but are not specific to chromoblastomycosis. [1] - This morphology indicates yeast proliferation but lacks the distinctive sclerotic appearance. *Negri body* - **Negri bodies** are eosinophilic, sharply demarcated neuronal cytoplasmic inclusions found in the diagnostic examination of **rabies** infection. - They are entirely unrelated to fungal infections like chromoblastomycosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 717.

Q: A skin biopsy shows 'snowstorm' appearance on polarized microscopy. Which histological finding would best confirm gouty tophi?

Needle-shaped crystals. ***Needle-shaped crystals*** - The "snowstorm" appearance on polarized microscopy, combined with the presence of **needle-shaped crystals**, is highly characteristic of **monosodium urate (MSU) crystals** seen in gouty tophi [1]. - These crystals typically show **strong negative birefringence** under polarized light [1]. *Rhomboid crystals* - **Rhomboid crystals** are characteristic of **calcium pyrophosphate dihydrate (CPPD) crystal deposition disease**, also known as pseudogout. - These crystals exhibit **positive birefringence**, differentiating them from MSU crystals. *Malta crosses* - **"Malta crosses"** are spherical aggregates of crystals, most commonly seen in **lipid-rich conditions**, such as cholesterol crystals in synovial fluid or fat emboli. - While they show birefringence, their morphology and association are distinct from gout. *Apple-green birefringence* - **Apple-green birefringence** is a characteristic finding in tissues stained with **Congo red** when viewed under polarized light, indicating the presence of **amyloid deposits**. - Amyloidosis is a protein misfolding disorder, unrelated to the crystal deposition seen in gout. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1218-1220.

Q: A skin biopsy shows 'tadpole' appearance of melanocytes. Which histological pattern would confirm Spitz nevus?

Kamino bodies. ***Kamino bodies*** - Kamino bodies are **eosinophilic globules** found within the epidermis of a Spitz nevus, particularly at the **dermo-epidermal junction**. - Their presence, along with the characteristic **'tadpole' appearance of melanocytes** (spindled and epithelioid cells in nests), strongly supports the diagnosis of Spitz nevus. *Civatte bodies* - **Civatte bodies** (also known as apoptotic keratinocytes) are typically seen in conditions involving **lichenoid inflammation**, such as **lichen planus** or **lupus erythematosus**. - They represent **apoptotic keratinocytes** that have undergone necrosis, not a specific feature of Spitz nevus. *Asteroid bodies* - **Asteroid bodies** are star-shaped inclusions found within **giant cells** in granulomatous conditions, most notably **sarcoidosis**. - They are composed of lipids and proteins and are not associated with melanocytic lesions like Spitz nevus. *Russell bodies* - **Russell bodies** are **eosinophilic, hyaline inclusions** found within plasma cells, representing accumulations of **immunoglobulins** in conditions like **plasmacytomas**. - They are not a feature of Spitz nevus or other melanocytic proliferations.

Q: A skin biopsy shows 'crown of thorns' pattern on immunofluorescence. Which additional finding would confirm IgA vasculitis?

Leukocytoclastic vasculitis. ***Leukocytoclastic vasculitis*** - **IgA vasculitis**, also known as Henoch-Schönlein purpura, is characterized by **leukocytoclastic vasculitis** on skin biopsy, which involves fragmentation of neutrophils and fibrinoid necrosis of vessel walls [1]. - The "crown of thorns" pattern on immunofluorescence refers to the **perivascular IgA deposition** seen in IgA vasculitis, which is pathognomonic when coupled with the histological finding of leukocytoclastic vasculitis. *Granulomatous inflammation* - This type of inflammation is characterized by aggregates of **macrophages** (histiocytes) and is typical of conditions like **tuberculosis**, sarcoidosis, or certain fungal infections, not IgA vasculitis. - **Granulomas** form as a defense mechanism to wall off foreign substances or pathogens that cannot be eliminated by other inflammatory responses. *Eosinophilic spongiosis* - **Eosinophilic spongiosis** is characterized by intercellular edema within the epidermis accompanied by **eosinophil infiltration**, typically seen in **allergic contact dermatitis**, drug reactions, or pemphigus. - This pattern reflects an allergic or hypersensitivity response rather than a vasculitic process, and is not a feature of IgA vasculitis. *Interface dermatitis* - **Interface dermatitis** is a pattern of inflammation at the dermo-epidermal junction, typically seen in conditions like **lichen planus**, lupus erythematosus, or erythema multiforme. - It is characterized by vacuolar degeneration of basal keratinocytes and a prominent lymphocytic infiltrate at the junction, which is fundamentally different from a vasculitic process. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Cardiovascular Disease, pp. 278-280.

Q: Munro's microabscesses are seen in all of the following except:

Pemphigus.. ***Pemphigus*** - **Pemphigus** is characterized by **acantholysis**, the dissolution of intercellular bridges between keratinocytes, leading to intraepidermal blister formation [1]. - While it involves inflammatory changes, the characteristic neutrophilic collections known as **Munro's microabscesses** (which are collections of neutrophils in the stratum corneum) are not a feature [4]. *Benign migratory glossitis* - Also known as **geographic tongue**, this condition can show histological features similar to psoriasis, including **Munro's microabscesses**. - It involves areas of **atrophic filiform papillae** surrounded by elevated white or yellowish borders, which histologically show features of chronic inflammation and neutrophil accumulation. *Psoriasis* - **Munro's microabscesses** are a classic histological hallmark of **psoriasis**, particularly in the pustular forms [3]. - They represent accumulations of **neutrophils in the stratum corneum** and indicate the inflammatory nature of the disease [2]. *Reiter syndrome* - **Reiter syndrome**, now often referred to as **reactive arthritis**, can present with dermatological manifestations such as **keratoderma blennorrhagicum**, which is histologically indistinguishable from **pustular psoriasis**. - Therefore, **Munro's microabscesses** can be found in the epidermal lesions associated with Reiter syndrome. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 645-646. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 640-641. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 636-637. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1172.

Q: Parakeratosis is defined as:

Retention of nuclei in stratum corneum. ***Retention of nuclei in stratum corneum*** - **Parakeratosis** is a histological term defining the abnormal retention of **nuclei** within the cells of the **stratum corneum** [1]. - This indicates incomplete or abnormal keratinization, where keratinocytes fail to fully mature and lose their nuclei as they reach the uppermost layer of the epidermis [1]. *Decreased thickness of stratum corneum* - A decreased thickness of the **stratum corneum** is referred to as **atrophy** or thinning, which is not the definition of parakeratosis. - This typically indicates a reduction in the number of cell layers, not the presence of nuclei within those layers. *Retention of cytoplasmic contents in stratum corneum* - While cells normally lose most of their cytoplasmic organelles during the keratinization process, the defining feature of parakeratosis specifically refers to the retention of the **nucleus**. - The presence of cytoplasmic contents without nuclei would not be termed parakeratosis. *Increased thickness in stratum corneum* - An increased thickness of the **stratum corneum** is known as **hyperkeratosis**. - Hyperkeratosis can occur with or without parakeratosis, but the presence of nuclei is the key characteristic of parakeratosis, not merely the thickness. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 640-641.

Question 1

HMB 45 is a tumor marker for which of the following neoplasms?

Accepted Answer

Malignant melanoma

Answer

Mesothelioma

Answer

Bronchogenic carcinoma

Answer

Pancreatic carcinoma

Question 2

All of the following are premalignant lesions except:

Accepted Answer

Rhinophyma

Answer

Giant Hairy Naevus

Answer

Actinic Solar Keratosis

Answer

Bowen’s Disease

Question 3

The skin biopsy shown below is most consistent with which of the following conditions?
![img-28.jpeg](img-28.jpeg)

Accepted Answer

Lichen planus

Answer

Lichen nitidus

Answer

Morphea

Answer

Lupus erythematosus

Question 4

A child presents with multiple skin lesions over the inner thigh and genital areas. It initially started as macule and later developed to become nodules. Some nodules have central umbilication. The histology of the lesion is shown below

Accepted Answer

Henderson-Patterson bodies

Answer

Guarnieri bodies

Answer

Cowdry type A inclusion bodies

Answer

Negri bodies

Question 5

Which of the following structures is pathognomonic for chromoblastomycosis?

Accepted Answer

Sclerotic body

Answer

Asteroid body

Answer

Budding yeast

Answer

Negri body

Question 6

A skin biopsy shows 'snowstorm' appearance on polarized microscopy. Which histological finding would best confirm gouty tophi?

Accepted Answer

Needle-shaped crystals

Answer

Rhomboid crystals

Answer

Malta crosses

Answer

Apple-green birefringence

Question 7

A skin biopsy shows 'tadpole' appearance of melanocytes. Which histological pattern would confirm Spitz nevus?

Accepted Answer

Kamino bodies

Answer

Civatte bodies

Answer

Asteroid bodies

Answer

Russell bodies

Question 8

A skin biopsy shows 'crown of thorns' pattern on immunofluorescence. Which additional finding would confirm IgA vasculitis?

Accepted Answer

Leukocytoclastic vasculitis

Answer

Granulomatous inflammation

Answer

Interface dermatitis

Answer

Eosinophilic spongiosis

Question 9

Munro's microabscesses are seen in all of the following except:

Accepted Answer

Pemphigus.

Answer

Benign migratory glossitis.

Answer

Psoriasis.

Answer

Reiter syndrome.

Question 10

Parakeratosis is defined as:

Accepted Answer

Retention of nuclei in stratum corneum

Answer

Decreased thickness of stratum corneum

Answer

Retention of cytoplasmic contents in stratum corneum

Answer

Increased thickness in stratum corneum

Dermatopathology — MCQs

Dermatopathology — MCQs

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